Hand held, portable computers have gained widespread acceptance in recent years. In various service and manufacturing businesses, hand held computers having interactive display screens are being utilized in production control and inventory control functions as well as product and package expediting. Hand held computers having relatively large interactive display screens are often referred to as workslate computers. The interactive display screen permits an operator of a workslate computer to input data and commands by appropriately touching the screen.
Some interactive display screens are touch sensitive, that is, input to the computer occurs when the screen receives directed pressure from the operator's finger or other appropriate object such as a pen or stylus. The display screen sensing circuitry detects the directed pressure using transducers or other sensing means and determines which portion of the display screen was touched. If a stylus is used in conjunction with a touch screen interactive display screen, the stylus itself does not perform any electronic function. Unfortunately, touch screen interactive display screens are not very durable and, therefore, are not well suited for many manufacturing, warehousing and package delivery environments where a workslate computer is prone to be bumped, dropped, etc.
As an alternative to a workslate computer with a touch screen interactive display screen, pen based workslate computers offer interactive display screen technologies which allow for a more durable construction. In pen based workslate computers, the pen or stylus is active, that is, when operational it generates a signal which when in proximity to the workslate computer interactive display screen is received by the workslate computer circuitry. Depending on the technology of the interactive display screen sensing circuitry, a distal tip of the pen or stylus may emit electromagnetic signals, radio frequency (rf) signals or acoustical signals which are received by sensing circuitry of the interactive display screen.
The sensing circuitry correlates the received signals to a position on the screen which corresponds to the position of the tip of the stylus on the screen. The position and movement of the pen is tracked and interpreted as a data or command input to the workslate computer microprocessor. Icons may be displayed to give the operator command options and the operator may select a command by appropriately touching the display screen surface with the stylus in the region where the icon corresponding to the desired command is located. A handwriting recognition module may be provided to enable the user to input data by "writing" on the display screen surface. A layer of tempered glass overlies the display screen. The tempered glass provides a durable layer of protection over a display surface of the display screen. The tempered glass is resistant to scratching and protects the sensing surface from damage if impacted by another object.
In order to generate appropriate signals, an electronic pen or stylus of a pen based workslate computer must include appropriate electronic circuitry and has to be coupled to a source of power. One way of supplying power to a electronic stylus is to tether the stylus to the computer's internal power source with a coiled power cord. Such a coiled power cord between the computer housing and the electronic stylus, however, tends to interfere with the operator's ability to use the stylus since the cord may wrap around a portion of the computer housing during use, become knotted or may lay on the display screen surface requiring the operator to push it out of the way to properly position the stylus on the display screen tempered glass surface. Adding a power cord retraction assembly increases the weight of the workslate computer and is prone to failure.
To avoid the use of a coiled or retractable power cord to power an electronic stylus, some styluses have been designed to receive one or more batteries internally which provide power to the stylus electronic circuitry. Typically, the batteries are watch batteries and are received in an interior region of the stylus housing which is accessible by removing a portion of the stylus housing from the remainder of the stylus. The batteries provide a finite working life for the stylus. Additionally, operators using such a stylus have a tendency to remove the removable portion of the stylus housing. This often results in the removable portion and/or the batteries being lost or damaged.
What is needed is a untethered or detachable stylus which has an increased useful life between battery changes and is less susceptible to damage due to repeated removal of a portion of the stylus housing.